Method for removing AlCl3 -based catalyst residues from polymer mixtures

ABSTRACT

A method is described for removing catalyst residues comprising AlCl 3  and/or its complexes from polymer products deriving from the (co)polymerization of olefinic cuts, the method comprising bringing the polymerized mass into contact with organometallic compounds, treating the resultant mixture with water or with aqueous acid or basic solutions, and separating the organic phase, which is substantially free of inorganic residues.

This invention relates to a method for removing catalyst residuescomprising AlCl₃ and/or its complexes from polymer products derivingfrom the Friedel-Crafts polymerization of ethylenically unsaturatedhydrocarbons or hydrocarbon mixtures.

The name Friedel-Crafts defines a various collection of reactions linkedtogether by the common use of cationic catalyst systems based on Al, Fe,Zn, B, Sn and other halides. These reactions include alkylation, ketonesynthesis, isomerization and polymerization, among many others.

For the purposes of the present invention, the Friedel-Crafts catalysisconsidered will be that involved in polymerization reactions initiatedby AlCl₃ -based catalyst systems. An example of polymerization initiatedby AlCl₃ -based systems is the polymerization of unsaturated hydrocarbonmixtures based on mainly C4, C5 and higher olefinic and diolefinicmonomers of aliphatic, cycloaliphatic and aromatic type.

Other examples of polymerization initiated by AlCl₃ -based systems arethe polymerization and copolymerization of natural monomers such asterpenes, with other unsaturated organic compounds. Such polymerizationsare generally conducted in continuous reactors, although batch orsemi-continuous reactors can also be used, in the although not strictlynecessary presence of an inert diluent, at a temperature generallyexceeding 0° C. These polymerizations enable hard and fragile resins tobe prepared suitable for use in formulations for adhesives, inks or oilssome of which have siccative characteristics, i.e. products withcharacteristics intermediate between resins and oils. The separation ofthe polymer from the reaction mixture requires the deactivation andremoval of the catalyst residues from it. The procedures indicated bythe prior art include aqueous acid, neutral and basic treatment, asindicated in U.S. Pat. No. 2,335,912, U.S. Pat. No. 2,391,293 and U.S.Pat. No. 1,938,320, and alcohol and ammonia treatment as indicated inU.S. Pat. No. 1,939,932 and U.S. Pat. No. 2,287,535. The commondrawbacks of these procedures are the ready formation of emulsions ifaqueous solutions are used, and contamination of the hydrocarbon solventif alcohol is used, and which must be removed before any reuse of thesolvent to avoid the formation of stable inactive complexes of it withAlCl₃.

Other known procedures include the use of oxides and hydroxides such asCaO, Ca(OH)₂, MgO and Mg(OH)₂, possibly in the presence of controlledquantities of water, as described in U.S. Pat. No. 2,734,892. In thiscase the drawbacks derive from the need to filter off a solid residuewhich can be in gelatinous form, and the accompanying difficultythereof.

It has also been found that using procedures of the known art, aconsistent quantity of the chlorine originally pertaining to the AlCl₃or to its complexes becomes bound in organic chloride form to thepolymer and to its unreacted monomers.

This fact gives rise both to a quality problem for the polymer, whichbecause it contains chlorine in organic form can release it as HClduring treatment and high temperature processing, with consequentequipment corrosion and colour degradation, and to a disposal problemfor possible effluent hydrocarbon mixtures, which as they containchlorine cannot be burned directly in normal combustion furnaces.

The object of the present invention is therefore to provide a method forremoving catalyst residues containing AlCl₃ or its complexes from theproducts of the Friedel-Crafts polymerization of ethylenicallyunsaturated hydrocarbon mixtures, which obviates the stated drawbacks ofthe known art.

A particular object of the present invention is to provide a methodwhich enables AlCl₃ -based catalyst residues to be removed fromunsaturated polymerization products without undesirable emulsionformation, and which results in a considerable reduction in the organicchlorine bound both to the polymer and to the effluent.

In accordance with the aforegoing, the present invention provides amethod for the removal of catalyst residues present in polymers preparedfrom olefinic hydrocarbons or their mixtures by a Friedel-Craftsreaction, the method comprising the following three basic operations:

treating the polymerized mixture with an organometallic compound,preferably a metal alkyl or a metal hydride;

treating the resultant mixture from the previous stage with water oraqueous solutions of acids or bases;

separating the desired organic phase.

Said method enables high purity polymers to be obtained, and which forman integral part of the present invention.

Specifically, in the method according to the present invention, anorganometallic reagent chosen from metal alkyls and metal hydrides of atleast one metal chosen from Al, Fe, Co, Ni, V etc. is added to the massresulting from the polymerization reaction, the reagent preferably beingat least one organometallic derivative of aluminum such as AlEt₃, AlEt₂Cl, AlEtCl₂, or Al(i-But)₂ H. The contact between the resultant mixturefrom the polymerization reaction and the aforesaid organometallicderivative is effected at a temperature of between -20° C. and +200° C.,and can be protracted with time while the reaction mass progressivelyclears. Water or an aqueous solution of an acid or base is then added tothe resultant product at the same temperature as that at which thereaction with the organometallic derivative is conducted, which ispreferably ambient temperature. Operating with solutions between 0.5 and5N is preferred, with absolute preference for normal sodium hydroxidesolutions.

The clarified organic phase free of inorganic residues is rapidlydecanted from the aqueous phase without emulsion formation, and theproducts contained in the organic phase, such as the polymer in the caseof a polymerization reaction, can be recovered by known methods.

As specified heretofore, only a small quantity of the organometallicreagent is used for contacting the catalyst residues. Anorganometallic/AlCl₃ molar ratio of between 0.5 and 2 can beconveniently used, although there are no restrictions on the use of ahigher ratio other than those dictated by economic reasons.

The practical reactant quantities to be used in the second stage of thedescribed method of the present invention are generally between 0.5times and twice the volume of the polymer mass to be treated.

If the protic solvent consists of dilute solutions of acids or bases,their concentration is generally less than 5N and preferably not greaterthan 2N.

Having described the general aspects of the invention, the followingexamples are provided to illustrate certain details thereof, but are inno case to be considered limitative.

Unless otherwise specified, all stated compositions and percentages areby weight.

EXAMPLE 1

1000 g of a selected cut of hydrocarbon monomers deriving from steamcracking having the following composition:

    ______________________________________                                        Component         wt %                                                        ______________________________________                                        1-butene          0.84                                                        1,3-butadiene     1.67                                                        butane            1.10                                                        trans-2-butene    1.14                                                        cis-2-butene      1.50                                                        1,2-butadiene     0.24                                                        3-methyl-1-butene 0.73                                                        isopentane        9.58                                                        1,4-pentadiene    1.46                                                        2-butyne          0.33                                                        1-pentene         3.44                                                        2-methyl-1-butene 5.14                                                        pentane           13.63                                                       isoprene          6.96                                                        trans-2-pentene   8.80                                                        cis-2-pentene     3.48                                                        2-methyl-2-butene 11.21                                                       trans-piperylene  3.65                                                        cyclopentadiene   0.24                                                        cis-piperylene    1.81                                                        cyclopentene      10.14                                                       dicyclopentadiene 8.70                                                        higher saturateds 4.21                                                        ______________________________________                                    

are fed into a glass rector of 2 liter volume fitted with a coolingjacket and a mechanical stirrer.

While maintaining the reaction mixture temperature at between 10° and20° C. by circulating cooling liquid, 12 g of AlCl₃ are fed, understirring, into the reactor in the form of a complex with HCl and xylenewhich has been prepared separately by bubbling hydrochloric acid gasinto a suspension of aluminium trichloride and xylene in a 1:1 molarratio and leaving to react for 3 hours.

On termination of polymerization the reaction mass is divided into 200 galiquots.

One 200 g aliquot is transferred into a 2 liter glass flask fitted witha mechanical stirrer and left in contact for 30 minutes under stirringwith 500 g of a 1M aqueous sodium hydroxide solution. The emulsifiedorganic phase is then decanted and washed repeatedly with distilledwater until neutral.

The neutralized organic phase is then heated to 230° C. under nitrogenat atmospheric pressure to separate the unreacted hydrocarbons and isthen stripped in a nitrogen stream at 40 mm Hg to separate the oligomersfrom the resin.

EXAMPLE 2

A 200 g aliquot of the reaction mass divided in Example 1 is left incontact with 4.82 g of diethylaluminium monochloride (C₂ H₅)₂ AlCl in a400 ml reactor under stirring at 90° C. for 1 hour. The reaction mixtureis cooled and then transferred into a 2 liter glass flask fitted with amechanical stirrer and left in contact for 30 minutes under stirringwith 500 ml of a 1M aqueous sodium hydroxide solution. The organicphase, which after decanting is clear, is heated to 230° C. undernitrogen at atmospheric pressure to separate the unreacted hydrocarbonsand is then stripped in a nitrogen stream at 40 mm Hg to separate theoligomers from the resin.

EXAMPLE 3

The procedure of example 2 is followed but using 3.81 g ofethylaluminium dichloride (C₂ H₅)AlCl₂.

EXAMPLE 4

The procedure of Example 2 is followed but using 2.84 g ofdiisobutylaluminium monohydride (i-C₄ H₉)₂ AlH.

The following table summarizes the results of the experiments describedin the examples.

    ______________________________________                                        Example No.      1       2       3     4                                      ______________________________________                                        Organometallic compound:                                                                              DEAC    EADC  DIBAH                                   Grams of organomet.      4.82    3.81   2.84                                  compound:                                                                     Resin softening point °C.:                                                              98     101      97    97                                     (ASTM E 28)                                                                   Resin Gardner colour (1):                                                                       7-     5+      5+     5+                                    Gardner colour 2 h/190° C.:                                                             10+     7+      7+     8-                                    Resin residual organic                                                                        2400    660     150   1100                                    chlorine ppm:                                                                 ______________________________________                                         (1) measured on a 50 wt % solution in toluene.                           

We claim:
 1. A method for removing catalyst residues comprising AlCl₃and/or its complexes from polymer products deriving from theFriedel-Crafts polymerization of olefinic hydrocarbons or mixturesthereof, said method comprising:a) treating the polymerized mixture withan organometallic compound; b) treating the resultant mixture with wateror an aqueous acid or basic solution to obtain an aqueous phase and anorganic phase; and c) separating the desired organic phase.
 2. A methodfor removing catalyst residues as claimed in claim 1, wherein theorganometallic compound used in stage a) is chosen from metal alkyls andmetal hydrides.
 3. A method for removing catalyst residues as claimed inclaim 2, wherein the organometallic compound is an aluminium compound.4. A method for removing catalyst residues as claimed in claim 3,wherein the aluminium compound is chosen from AlEt₃, AlEt₂ Cl, AlEtCl₂and Al(i-But)₂ H.
 5. A method for removing catalyst residues as claimedin claim 1, wherein the treatment under a) is conducted in the presenceof a quantity of organometallic compound such that the molar ratio ofthe organometallic compound to the Friedel-Crafts catalyst is between0.5 and
 2. 6. A method for removing catalyst residues as claimed inclaim 1, wherein the treatment under a) is conducted at a temperaturechosen within the range of -20° C. to +200° C.
 7. A method for removingcatalyst residues as claimed in claim 1, wherein the treatment under b)is conducted with an aqueous acid or basic solution at a concentrationof between 0.5 and 5N.
 8. A method for removing catalyst residues asclaimed in claim 7, wherein the treatment is conducted with a normalsodium hydroxide solution.
 9. A method for removing catalyst residues asclaimed in claim 1, wherein the treatment under a) is conducted atambient temperature.
 10. A method for removing catalyst residues asclaimed in claim 1, wherein the treatment under b) is conducted in thepresence of an amount of water or aqueous acid or basic solution ofbetween 0.5 and 2 times the volume of the polymer mass to be treated.11. A method for removing catalyst residues as claimed in claim 1,wherein the separation under c) is conducted by decantation.
 12. Amethod for removing catalyst residues as claimed in claim 1, wherein thetreated polymer mass is derived from a Friedel-Crafts polymerization,and wherein the reactants fed to the polymerization are ethylenicallyunsaturated hydrocarbons obtained from steam cracking, or unsaturatedterpene hydrocarbons.
 13. A method for removing catalyst residues asclaimed in claim 2, wherein the organometallic compound is chosen fromaluminum, iron, cobalt, nickel, and vanadium compounds.
 14. A method forremoving catalyst residues as claimed in claim 4, wherein the treatmentwith the aluminum compound is conducted at about 90° C. for about 1hour.